With advances in technology, development of wearable computers has accelerated. Wearable computers refer to computers that a user can naturally wear like clothes, wristwatches, glasses, or accessories. Although smart phones and tablet PCs may be conveniently used using user fingers or a touch pen, they may be inconvenient in that the user has to put them in a pocket or bag or carry such devices. On the contrary, the user can wear a wearable computer on the wrist or on the eyes like glasses, thereby providing convenience in mobility relative to the smart phone or tablet PC. In particular, among wearable computers, a variety of wristwatch related products, for example, a smart watch, capable of wirelessly providing various services such as weather forecasts, messages, notifications, stock quotes, etc., have been emerged.
Meanwhile, a smart watch may be interlinked with an external digital device such as a smart phone. If an event occurs in the smart watch or an external digital device, whether the smart watch or the external digital device will notify a user of the event needs to be determined.